Paul Scherrer Institut, Villigen, Switzerland.
J Phys Chem A. 2011 Nov 24;115(46):13443-51. doi: 10.1021/jp208018r. Epub 2011 Oct 21.
Internal energy selected bromofluoromethane cations were prepared and their internal energy dependent fragmentation pathways were recorded by imaging photoelectron photoion coincidence spectroscopy (iPEPICO). The first dissociation reaction is bromine atom loss, which is followed by fluorine atom loss in CF(3)Br and CF(2)Br(2) at higher energies. Accurate 0 K appearance energies have been obtained for these processes, which are complemented by ab initio isodesmic reaction energy calculations. A thermochemical network is set up to obtain updated heats of formation of the samples and their dissociative photoionization products. Several computational methods have been benchmarked against the well-known interhalogen heats of formation. As a corollary, we stumbled upon an assignment issue for the ClF heat of formation leading to a 5.7 kJ mol(-1) error, resolved some time ago, but still lacking closure because of outdated compilations. Our CF(3)(+) appearance energy from CF(3)Br confirms the measurements of Asher and Ruscic (J. Chem. Phys. 1997, 106, 210) and Garcia et al. (J. Phys. Chem. A 2001, 105, 8296) as opposed to the most recent result of Clay et al. (J. Phys. Chem. A 2005, 109, 1541). The ionization energy of CF(3) is determined to be 9.02-9.08 eV on the basis of a previous CF(3)-Br neutral bond energy and the CF(3) heat of formation, respectively. We also show that the breakdown diagram of CFBr(3)(+), a weakly bound parent ion, can be used to obtain the accurate adiabatic ionization energy of the neutral of 10.625 ± 0.010 eV. The updated 298 K enthalpies of formation Δ(f)H(o)(g) for CF(3)Br, CF(2)Br(2), CFBr(3), and CBr(4) are reported to be -647.0 ± 3.5, -361.0 ± 7.4, -111.6 ± 7.7, and 113.7 ± 4 kJ mol(-1), respectively.
通过成像光电离电子符合光谱（iPEPICO），制备了内能选择的溴氟甲烷阳离子，并记录了它们的内能依赖的碎裂途径。第一个离解反应是溴原子的损失，在更高的能量下，CF(3)Br 和 CF(2)Br(2) 中接着是氟原子的损失。已经获得了这些过程的准确的 0 K 表观能，并用从头计算的等电子反应能计算进行了补充。建立了一个热化学网络，以获得样品及其解离光致电离产物的更新生成热。几种计算方法与著名的卤素间化合物生成热进行了基准测试。作为推论，我们偶然发现了 ClF 生成热的归属问题，导致 5.7 kJ mol(-1) 的误差，这个问题在一段时间前得到了解决，但由于过时的汇编，仍然没有得到解决。我们从 CF(3)Br 得到的 CF(3)(+)的表观能证实了 Asher 和 Ruscic（J. Chem. Phys. 1997, 106, 210）和 Garcia 等人（J. Phys. Chem. A 2001, 105, 8296）的测量结果，而不是 Clay 等人（J. Phys. Chem. A 2005, 109, 1541）的最近结果。基于之前的 CF(3)-Br 中性键能和 CF(3)生成热，分别确定 CF(3)的电离能为 9.02-9.08 eV。我们还表明，可以使用 CFBr(3)(+)的分解图，即一个弱束缚的母体离子，来获得中性的准确绝热电离能，为 10.625 ± 0.010 eV。报告了 CF(3)Br、CF(2)Br(2)、CFBr(3)和 CBr(4)的更新的 298 K 生成焓Δ(f)H(o)(g)分别为-647.0 ± 3.5、-361.0 ± 7.4、-111.6 ± 7.7 和 113.7 ± 4 kJ mol(-1)。
